JP2009088206A - Method for manufacturing rare earth magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a rare earth magnet that can obtain the sufficient adhesion strength between a magnet element assembly and a copper plated layer. <P>SOLUTION: The present invention relates to the method for manufacturing the rare earth magnet that has the magnet material body containing rare earth elements and the copper plated layer formed on the surface of the magnet material body; and the method includes a pretreatment process to adhere preprocessing solution including potassium pyrophosphate and/or sodium pyrophosphate with an ion concentration of the pyrophosphate acid of no less than 60 g/L, and a plating process that forms the copper plated layer on the surface of the magnet material body by performing plating using copper plating liquid containing copper ion and pyrophosphoric acid ion on the magnet material body subjected to pretreatment process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rare earth magnet, and more particularly, to a method for producing a rare earth magnet having a plating layer formed on the surface thereof.

  Rare earth magnets containing rare earth elements have an excellent magnetic force and are used in a wide range of applications. This rare earth magnet tends to have low corrosion resistance because it contains a rare-earth element that is easily oxidized as a main component, and it is generally configured that a protective layer is provided on the surface of a magnet body having magnetic properties. Is.

As such a protective layer, since sufficient corrosion resistance can be provided and formation of the protective layer is relatively easy, a copper plating layer is frequently used. In a rare earth magnet having a copper plating layer on its surface, it is important to suppress cracking, swelling, or peeling of the copper plating layer from the viewpoint of maintaining excellent corrosion resistance. Therefore, Patent Document 1 below discloses a rare-earth magnet in which a copper plating layer (copper plating film) having a specific two-layer structure is formed in order to suppress these problems. Further, this document shows that a plating pretreatment using an aqueous solution containing 1 to 10 wt% of potassium pyrophosphate or sodium pyrophosphate is performed before the formation of the first copper plating layer.
JP 2002-198240 A

  However, as a result of investigations by the present inventors, it has been found that it is still difficult to obtain sufficient adhesion strength between the magnet body and the plating layer in the conventional rare earth magnet described above. In particular, in recent years, rare earth magnets are increasingly used under severe conditions such as high temperatures. Under such severe conditions, the adhesion strength obtained by the above-described conventional method can prevent the plating layer from peeling off. Sufficient suppression tends to be more difficult.

  Then, this invention is made | formed in view of such a situation, and it aims at providing the manufacturing method of the rare earth magnet which can fully obtain the adhesive strength of a magnet element body and a copper plating layer. .

  In order to achieve the above object, a method for producing a rare earth magnet of the present invention is a method for producing a rare earth magnet having a magnet body containing a rare earth element and a copper plating layer formed on the surface of the magnet body. A pretreatment step of attaching a pretreatment liquid containing potassium pyrophosphate and / or sodium pyrophosphate and having a pyrophosphate ion concentration of 60 g / L or more to the magnet body, and a magnet after the pretreatment step The element body is plated with a copper plating solution containing copper ions and pyrophosphate ions to form a copper plating layer on the surface of the magnet element body.

  The formation of the plating layer on the surface of the magnet body of the rare earth magnet is generally performed by plating using a copper plating solution containing copper ions. However, since copper is an element that is more likely to be in an electrically neutral state than an ionized state, in the above plating, copper is deposited on the surface of the magnet body by plating. In some cases, the copper contained in the copper plating solution may be replaced with an element in the magnet body. Therefore, in the conventional method, it is difficult for the copper plating layer to adhere uniformly to the magnet body, and as a result, the adhesion strength between the magnet body and the copper plating layer is insufficient.

  Thus, it is known that when pyrophosphate ions coexist in the copper plating solution, it is possible to suppress substitution of copper with elements of the magnet body. However, in this case, if the substitution of copper is suppressed by increasing the concentration of pyrophosphate ions in order to obtain higher adhesion strength than before, there is a tendency that copper plating is not sufficiently generated.

  In contrast, in the present invention, before performing the plating step using the copper plating solution containing copper ions and pyrophosphate ions, potassium pyrophosphate and sodium pyrophosphate are contained, and the concentration of pyrophosphate ions based on these. Is performing a pretreatment step using a pretreatment liquid having a certain value or more. Therefore, at the initial stage of the plating process, the concentration of pyrophosphate ions in the copper plating solution becomes sufficiently high due to the pretreatment liquid adhering to the surface of the magnet body, which allows the elements of copper and the magnet body to be The substitution of is favorably suppressed. As a result, in the present invention, copper plating is preferentially generated in the plating step, and the adhesion strength between the magnet body and the copper plating layer is improved satisfactorily.

  In addition, according to the manufacturing method of the present invention, since a high concentration of pyrophosphoric acid may be attached in the pretreatment process, the concentration of pyrophosphate ions in the copper plating solution used in the plating process should be within a practical range. Can do. Therefore, in the present invention, copper plating is hardly inhibited by pyrophosphate ions contained in excess during the plating step, and a sufficient plating rate can be obtained.

  In the method for producing a rare earth magnet of the present invention, the concentration of pyrophosphate ions in the pretreatment liquid is preferably 1.2 times or less than the concentration of pyrophosphate ions in the copper plating solution. By using a pretreatment solution and a copper plating solution that satisfy these conditions, the change in pyrophosphate ion concentration in the copper plating solution does not occur excessively during the plating process, and stable copper plating can be performed. It becomes. As a result, it is possible to form a copper plating layer more satisfactorily on the surface of the magnet body.

  In the pretreatment step, it is preferable to use a cooled pretreatment liquid. Replacement of copper with the element of the magnet element tends to occur when the temperature is high. Therefore, by pre-cooled pretreatment liquid, the replacement with copper is further performed at the initial stage of the plating process. Can be reduced. As a result, the adhesion strength between the magnet body and the plating layer can be further improved.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the manufacturing method of the rare earth magnet which can fully obtain the adhesive strength of a magnet element body and a copper plating layer, and can obtain sufficient copper plating rate. .

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as necessary.

  FIG. 1 is a perspective view showing an example of a rare earth magnet obtained by the production method of the present invention. Moreover, FIG. 2 is a figure which shows typically the cross-sectional structure which follows the II-II line | wire of the rare earth magnet shown in FIG. As shown in the figure, the rare earth magnet 1 is composed of a magnet body 2 and a copper plating layer 4 formed on the surface thereof, and has a substantially rectangular parallelepiped shape as a whole.

  The magnet body 2 is a permanent magnet containing a rare earth element, and a composition known as a rare earth magnet can be applied without particular limitation. The copper plating layer 4 is a protective layer for protecting the magnet element body 2 in the rare earth magnet 1 and is made of copper deposited on the surface of the magnet element body 2 by plating.

  Here, the configuration of the magnet body 2 will be described in more detail. The rare earth elements contained in the magnet body 2 refer to scandium (Sc), yttrium (Y), and lanthanoid elements belonging to Group 3 of the long-period periodic table. Examples of the lanthanoid element include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium. (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and the like are included.

  Examples of the constituent material of the magnet body 2 include a material containing the rare earth element and a transition element other than the rare earth element in combination. In this case, as the rare earth element, at least one element selected from the group consisting of Nd, Sm, Dy, Pr, Ho and Tb is preferable, and these elements include La, Ce, Gd, Er, Eu, Tm, Yb and More preferably, it further contains at least one element selected from the group consisting of Y.

  As transition elements other than rare earth elements, iron (Fe), cobalt (Co), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu) At least one element selected from the group consisting of zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta) and tungsten (W) is preferable, and Fe and / or Co are more preferable. preferable.

  More specifically, examples of the constituent material of the magnet body 2 include R—Fe—B and R—Co materials. In the former constituent material, R is preferably a rare earth element mainly composed of Nd. In the latter constituent material, R is preferably a rare earth element mainly composed of Sm.

  As a constituent material of the magnet body 2, an R—Fe—B constituent material is particularly preferable. When the magnet body 2 is of the R-Fe-B type, conventionally, when the copper plating layer 4 is formed on the surface, the substitution of copper with Fe in the magnet body is extremely likely to occur. The adhesion between the element body and the copper plating layer 4 tended to be particularly deteriorated. On the other hand, according to the manufacturing method of the present invention as will be described later, such a decrease in adhesion can be reduced particularly well, so that the magnet body 2 has an R-Fe-B composition. In particular, the production method of the present invention is particularly suitable.

  The R-Fe-B-based magnet element body 2 has a main phase with a substantially tetragonal crystal structure, and a rare earth-rich phase having a high rare earth element content in the grain boundary portion of the main phase, and boron It has a structure having a boron-rich phase with a high proportion of atoms. These rare earth-rich phase and boron-rich phase are nonmagnetic phases that do not have magnetism. Such a nonmagnetic phase is usually contained in an amount of 0.5 to 50% by volume in the magnet constituting material. Moreover, the particle size of the main phase is usually about 1 to 100 μm.

  In such R—Fe—B-based constituent materials, the rare earth element content is preferably 8 to 40 atomic%. When the rare earth element content is less than 8 atomic%, the crystal structure of the main phase becomes almost the same as that of α-iron, and the coercive force (iHc) tends to decrease. On the other hand, if it exceeds 40 atomic%, a rare earth-rich phase is excessively formed, and the residual magnetic flux density (Br) tends to be small.

  Further, the Fe content is preferably 42 to 90 atomic%. When the Fe content is less than 42 atomic%, Br decreases, and when it exceeds 90 atomic%, iHc tends to decrease. Furthermore, the content of B is preferably 2 to 28 atomic%. If the B content is less than 2 atomic%, a rhombohedral structure is likely to be formed, and this tends to reduce iHc. On the other hand, if it exceeds 28 atomic%, a boron-rich phase is excessively formed, and this tends to decrease Br.

  In the constituent materials described above, a part of Fe in the R—Fe—B system may be substituted with Co. Thus, if a part of Fe is replaced by Co, the temperature characteristics can be improved without deteriorating the magnetic characteristics. In this case, it is desirable that the amount of substitution of Co not be larger than the content of Fe. If the Co content exceeds the Fe content, the magnetic properties of the magnet body 2 tend to deteriorate.

  A part of B in the constituent material may be substituted with an element such as carbon (C), phosphorus (P), sulfur (S) or copper (Cu). By replacing a part of B in this way, the magnet body can be easily manufactured and the manufacturing cost can be reduced. At this time, the substitution amount of these elements is desirably an amount that does not substantially affect the magnetic properties, and is preferably 4 atomic% or less with respect to the total amount of constituent atoms.

  Further, from the viewpoint of improving iHc and reducing manufacturing costs, in addition to the above-described structure, aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), bismuth (Bi) Niobium (Nb), Tantalum (Ta), Molybdenum (Mo), Tungsten (W), Antimony (Sb), Germanium (Ge), Tin (Sn), Zirconium (Zr), Nickel (Ni), Silicon (Si) Further, elements such as gallium (Ga), copper (Cu), and hafnium (Hf) may be added. These addition amounts are also preferably in a range that does not affect the magnetic properties, and are preferably 10 atomic% or less with respect to the total amount of constituent atoms. In addition, oxygen (O), nitrogen (N), carbon (C), calcium (Ca), and the like are conceivable as components inevitably mixed, and these are about 3 atomic% or less with respect to the total amount of constituent atoms. It may be contained in an amount of.

  Next, a preferred embodiment of a method for producing a rare earth magnet having the above-described configuration will be described. FIG. 3 is a flowchart showing a manufacturing process of a rare earth magnet according to a preferred embodiment.

First, the magnet body 2 can be manufactured by a powder metallurgy method. In this method, first, an alloy having a desired composition is manufactured by a known alloy manufacturing process such as a casting method or a strip casting method (step S11). Next, this alloy is pulverized (coarse pulverization) to a particle size of 10 to 100 μm using a coarse pulverizer such as a jaw crusher, a brown mill, a stamp mill, etc. Finely pulverize to a particle size of 0.5 to 5 μm using a machine (step S12). Then, the powder thus obtained is preferably molded at a pressure of 0.5 to ⁵ t / cm ² in a magnetic field having a magnetic field strength of 600 kA / m or more to obtain a molded body (step S13).

  Thereafter, the obtained molded body is preferably fired in an inert gas atmosphere or in a vacuum at 1000 to 1200 ° C. for 0.5 to 10 hours (step S14). After firing, the obtained sintered body may be quenched. Furthermore, this sintered body is subjected to heat treatment at 500 to 900 ° C. for 1 to 5 hours in an inert gas atmosphere or in a vacuum, if necessary, and the sintered body is cut or polished to have a desired shape. The magnet element body 2 is obtained by processing into a (practical shape).

  The magnet body 2 obtained in this manner is appropriately cleaned to remove surface irregularities and impurities adhering to the surface (step S15). The cleaning is preferably, for example, acid cleaning using an acid solution. According to the acid cleaning, it is easy to obtain the magnet body 2 having a smooth surface by dissolving and removing irregularities and impurities on the surface of the magnet body 2.

  Nitric acid is preferred as the acid used in this acid cleaning. When plating a general steel material, non-oxidizing acids such as hydrochloric acid and sulfuric acid are often used. However, when the rare earth element is contained like the magnet body 2, if these acids are used for the treatment, hydrogen generated by the acid is occluded on the surface of the magnet body 2 and the occlusion site becomes brittle. A large amount of powdery undissolved material may be generated. This powdery undissolved material is not desirable because it may cause surface roughness, defects, poor adhesion and the like after the surface treatment. Therefore, it is preferable not to include the non-oxidizing acid described above in the treatment liquid used for the acid cleaning. Therefore, in this embodiment, it is preferable to use nitric acid, which is an oxidizing acid that generates little hydrogen.

  When nitric acid is used for the acid cleaning, the nitric acid concentration in the treatment liquid is preferably 1 N or less, particularly preferably 0.5 N or less. If the concentration of nitric acid is too high, the dissolution rate of the magnet body 2 becomes too fast and it becomes difficult to control the amount of dissolution, especially in large-scale processing such as barrel processing, and it is difficult to maintain the dimensional accuracy of the product. Tend to be. On the other hand, if the nitric acid concentration is too low, the amount of dissolution tends to be insufficient. For this reason, the nitric acid concentration is preferably 1 N or less, and particularly preferably 0.5 to 0.05 N. The amount of Fe dissolved at the end of the treatment is preferably about 1 to 10 g / l.

  The amount of dissolution of the surface of the magnet body 2 by such acid cleaning is preferably 5 μm or more, preferably 10 to 15 μm in average thickness from the surface. By so doing, the deteriorated layer and the oxide layer due to the processing of the surface of the magnet body 2 can be removed almost completely, and the desired copper plating layer 4 can be formed with higher accuracy in the plating step described later.

  In addition, after removing the treatment liquid used for the acid cleaning by washing with water after the above acid cleaning, the magnet body 2 has an ultra-thin structure in order to completely remove a small amount of undissolved substances and residual acid components remaining on the surface. It is preferable to perform cleaning using sonic waves. This ultrasonic cleaning can be performed, for example, in pure water, an alkaline solution, or the like that has very little chlorine ions that generate rust on the surface of the magnet body 2. After the ultrasonic cleaning, water cleaning may be performed as necessary.

  After producing the magnet body 2 as described above, the obtained magnet body contains potassium pyrophosphate and / or sodium pyrophosphate, and before the pyrophosphate ion concentration is 60 g / L or more. A pretreatment (plating pretreatment) for attaching the treatment liquid is performed (step S16; pretreatment step).

  In this pretreatment process, in order to adhere the pretreatment liquid to the surface of the magnet body 2, for example, the pretreatment liquid is dropped or sprayed on the surface of the magnet body 2, or the magnet body 2 is placed in the pretreatment liquid. Soak. From the viewpoint of uniformly attaching the pretreatment liquid to the entire surface of the magnet body 2, it is preferable to immerse the magnet body 2 in the pretreatment liquid.

  The pretreatment liquid is a solution containing one or both of potassium pyrophosphate and sodium pyrophosphate, and a solution containing potassium pyrophosphate is more preferable. The pretreatment liquid is preferably an aqueous solution in which these are dissolved in water. The pretreatment liquid may further contain ammonia, an organic amine compound, an organic carboxylate, and the like as long as the effects of the present invention are not impaired.

  The concentration of pyrophosphate ions in the pretreatment liquid is 60 g / L or more, preferably 80 g / L or more, and more preferably 100 g / L or more. When the concentration of pyrophosphate ions in the pretreatment liquid is less than 60 g / L, in the plating step described later, substitution of copper with elements in the magnet body cannot be sufficiently suppressed, and the magnet body 2 and the copper plating are performed. The adhesion strength with the layer 4 becomes insufficient.

  Moreover, the upper limit value of the pyrophosphate ion concentration in the pretreatment liquid is preferably 500 g / L, and more preferably 300 g / L. In the case of an aqueous solution, the concentration of pyrophosphate ions is almost saturated at 500 g / L, so it is difficult to increase the concentration further. In practice, since a sufficient effect is obtained at 300 g / L or less, if it is more than this, the use of an excessive amount of potassium pyrophosphate or sodium may increase the production cost of the rare earth magnet. The “concentration of pyrophosphate ion” is a value obtained by converting the amount of potassium or sodium pyrophosphate dissolved in the pretreatment liquid into “pyrophosphate ion”.

  In the pretreatment step, it is preferable to use a cooled pretreatment liquid. That is, the temperature of the pretreatment liquid is preferably lower than at least the copper plating liquid used in the plating step described later, more preferably lower than room temperature, and still more preferably 5 ° C. lower than room temperature. Specifically, the temperature of the pretreatment liquid is preferably −5 to 25 ° C., more preferably 5 to 20 ° C., and still more preferably 5 to 18 ° C. By using the cooled pretreatment liquid in this way, it is possible to further suppress substitution of copper and elements in the magnet body in the plating step described later. However, if the temperature of the pretreatment solution is too low, the temperature of the copper plating solution in the plating process becomes low or unstable, so that a sufficient plating rate cannot be obtained, and the uniform plating layer 4 is formed. May be difficult.

  After such a pretreatment process, the copper body containing copper ions and pyrophosphate ions is directly applied to the magnet body 2 without performing cleaning or the like that removes the pretreatment liquid adhering to the surface of the magnet body 2. Copper plating using a liquid is performed (step S17; plating step).

Copper plating can be performed by electrolytic plating. Specifically, for example, after the pre-processed magnet body 2 is immersed in a copper plating solution, a current of about 0.1 to 5.0 A / dm ² is passed with the magnet body 2 as the cathode side. Thus, copper ions in the copper plating solution are deposited on the surface of the magnet body 2, thereby forming the copper plating layer 4.

  Although the copper ion and pyrophosphate ion contained in the copper plating solution are not particularly limited, for example, they are formed by dissolving these salts. That is, examples of the copper plating solution include a solution obtained by dissolving a copper salt or pyrophosphate, and an aqueous solution obtained by dissolving these in water is particularly preferable.

  Examples of the copper ion raw material include copper inorganic acid salts and organic acid salts. Examples of the pyrophosphate ion raw material include metal pyrophosphates, and examples of the metal include potassium, sodium, and calcium. Of these, copper pyrophosphate is preferred as a raw material for copper ions. In this case, the pyrophosphate ion raw material does not have to be added, but when a pyrophosphate of a metal other than copper, for example, potassium pyrophosphate or sodium pyrophosphate is further added as a pyrophosphate ion raw material, It becomes possible to deposit copper more stably.

  The copper plating solution may contain a plurality of types of the above-described copper ions and pyrophosphate ions. The copper plating solution may further contain other components as required in addition to the raw materials for copper ions and pyrophosphate ions. Examples of such other components include ammonia, an organic amine compound, an organic carboxylate, and the like, and it is desirable to add them to the extent that copper plating is not hindered in the plating step.

  The concentration of copper ions in the copper plating solution is preferably 2 to 30 g / L. The concentration of pyrophosphate ions is preferably 50 to 200 g / L. In particular, in a copper plating solution, the ratio of pyrophosphate ion concentration to copper ion concentration (pyrophosphate ion concentration / copper ion concentration: hereinafter referred to as “P ratio”) is preferably 6 to 35, and is preferably 15 to 30. More preferably. By satisfying such a P ratio, a sufficient copper plating rate can be obtained while suppressing replacement of the element of the magnet body with copper during copper plating. Note that the concentrations of copper ions and pyrophosphate ions in the copper plating solution are values obtained by converting from the amounts of these raw materials added, as described above. When copper pyrophosphate is used as a copper ion raw material, the concentration of pyrophosphate ions includes the amount of pyrophosphate ions derived from the copper ion raw material.

  The P ratio is preferably as high as possible in order to suppress substitution of the element of the magnet body with copper during copper plating. However, if the P ratio of the copper plating solution is too high, It is practically difficult to set the P ratio of the copper plating solution to 35 or more because the speed may be extremely reduced or the copper plating film formation by electroplating may be insufficient. However, replacement of the element of the magnet body with copper during copper plating is a phenomenon that occurs particularly in the initial stage of the plating process. Therefore, in order to reduce this replacement, it is only necessary to increase the P ratio in the initial stage of the plating process. And in the manufacturing method of this invention, the density | concentration of the pyrophosphate ion of the surface layer vicinity of a magnet element body becomes high enough with the pre-processing liquid previously adhered to the surface of the magnet element body at the initial stage of a plating process. The P ratio in the vicinity of the surface layer of the magnet body in the initial stage of the plating process is several times the P ratio of the copper plating solution, and specifically, 40 or more can be realized. On the other hand, in the plating process after this initial stage, the copper ions in the copper plating solution need to diffuse in the pretreatment liquid adhering to the surface of the magnet body to reach the vicinity of the surface of the magnet body. The copper ion concentration in the vicinity of the surface layer of the element body is kept sufficiently low. As a result, even if the P ratio is as described above, a sufficient copper plating rate or the like can be obtained while suppressing the substitution of copper.

  As described above, the pretreatment liquid also contains pyrophosphate ions derived from sodium or potassium pyrophosphate. The concentration of pyrophosphate ions in the pretreatment liquid is preferably 1.2 times or less and more preferably 1.0 times or less with respect to the concentration of pyrophosphate ions in the copper plating solution used in the plating step. preferable. When the concentration of pyrophosphate ions in the pretreatment solution exceeds 1.2 times the concentration of pyrophosphate ions in the copper plating solution, the concentration of pyrophosphate ions in the copper plating solution is also affected. There is a possibility that the plating process does not proceed well, for example, a suitable P ratio of the copper plating solution described above cannot be obtained.

  On the other hand, if the pyrophosphate ion concentration in the pretreatment solution is too small compared to the pyrophosphate ion concentration in the copper plating solution, sufficient replacement of the copper in the copper plating solution with the elements in the magnet body in the plating process May not be able to be reduced. Also, for example, when the pretreatment liquid is used repeatedly, the pyrophosphate ion concentration in the pretreatment liquid gradually decreases and may eventually affect the pyrophosphate ion concentration in the copper plating solution. It is desirable to add pyrophosphate as appropriate to the copper plating solution. However, if the pyrophosphate ion concentration in the pretreatment solution is 0.3 times or more than the pyrophosphate ion concentration in the copper plating solution, a sufficient effect can be obtained, and the pyrophosphate concentration in the copper plating solution can be obtained. Since the ion concentration is also maintained well, such additional work can be omitted.

  The temperature of the copper plating solution in the plating step is preferably 15 to 60 ° C, and more preferably 20 to 50 ° C. If the temperature of the copper plating solution is too low, a sufficient copper plating rate cannot be obtained, and it may take time to form the copper plating layer 4 or it may be difficult to form the uniform copper plating layer 4. . In addition, if the temperature is too high, the copper plating rate becomes excessively high, and the control of the film thickness of the copper plating layer 4 tends to be difficult, and the copper in the copper plating solution and the elements in the magnet body There is also a possibility that the substitution cannot be sufficiently suppressed.

  From the viewpoint of obtaining sufficient corrosion resistance, the thickness of the copper plating layer 4 formed in the plating step is preferably 1 to 20 μm, and more preferably 2 to 15 μm. In the plating step, it is preferable to adjust the conditions such as the concentration of each component, the time of the plating step, the temperature of the plating solution, etc. so that the copper plating layer 4 having such a thickness is formed.

  A structure in which the copper plating layer 4 is formed on the surface of the magnet body 2 by such a plating process, thereby forming the copper plating layer 4 on the surface of the magnet body 2 as shown in FIGS. A rare earth magnet 1 having the following is obtained. In addition, after the plating step, the surface of the copper plating layer 4 may be cleaned by washing with water or the like.

  The preferred embodiments of the present invention have been described above. However, the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  For example, the structure of the rare earth magnet obtained by the manufacturing method of the present invention is not limited to that of the above-described embodiment. For example, another protective layer may be further formed on the surface of the copper plating layer 4. Further, the shape of the rare earth magnet is not limited to a rectangular parallelepiped shape, and may have various shapes such as a cubic shape and a cylindrical shape.

  Furthermore, in the method for producing a rare earth magnet of the present invention, as long as the pretreatment process is performed before the plating process is performed on the magnet body, even if some processes are omitted from the above embodiment, other processes are added. May be. For example, in the above-described embodiment, after the pretreatment process for the magnet body, the plating process is performed continuously. However, after the pretreatment process, the pretreatment liquid is not removed from the surface of the magnet body, or appropriately. As long as it remains, an appropriate treatment such as washing may be performed on the magnet body after the pretreatment.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[Preparation of rare earth magnets]

Example 1
An ingot having a composition of 27.4Nd-3Dy-1B-68.6Fe (number is mass%) prepared by a powder metallurgy method was pulverized by a stamp mill and a ball mill to obtain an alloy fine powder having the above composition. The obtained alloy fine powder was press-molded in a magnetic field to obtain a compact. After sintering this molded body under the conditions of a holding temperature of 1100 ° C. and a holding time of 1 hour, the molded body was further subjected to an aging treatment in an Ar gas atmosphere under a holding temperature of 600 ° C. and a holding time of 2 hours. Thus, a sintered body was obtained. Then, the obtained sintered body was processed into a size of 30 × 20 × 2 (mm), and further chamfered by barrel polishing to obtain a magnet body. Thereafter, the magnet body was subjected to alkaline degreasing treatment, water washing, acid washing treatment with a nitric acid solution, water washing, smut removal treatment by ultrasonic washing, and water washing in this order.

  Then, an aqueous solution having a potassium pyrophosphate concentration of 120 g / L was prepared as a plating pretreatment liquid, and the liquid temperature was adjusted to 18 ° C. or 25 ° C. The pretreatment solution has a pyrophosphate ion concentration of 63.3 g / L. Next, a pretreatment for plating in which the magnet body obtained above was immersed in this pretreatment liquid for 5 minutes was performed.

Thereafter, a copper plating solution having the following composition was prepared and adjusted to pH 10.5 and a bath temperature of 40 ° C. The magnet body after the pretreatment described above is immersed in this copper plating solution without being washed, and the thickness of the Cu plating film is 8 μm with respect to this magnet body under a current density of 0.2 A / dm ^2. Then, electroplating was performed until a rare earth magnet having a copper plating layer formed on the surface of the magnet body was obtained. The composition of the copper plating solution is as follows.
Potassium pyrophosphate: 200 g / L
Copper pyrophosphate trihydrate: 10 g / L
Potassium citrate: 60.0 g / L
28% ammonia water: 1.0 mL / L

  The pyrophosphate ion concentration in the copper plating solution is 110 g / L, and the pyrophosphate ion concentration in the pretreatment solution is 63.3 g / L. These ratios, that is, pyrophosphate in the pretreatment solution The value of ion concentration / pyrophosphate ion concentration in the copper plating solution (hereinafter referred to as “pyrophosphate ion concentration ratio”) was 0.53. This value is also shown in Table 1 (the same applies to the following examples and comparative examples).

(Examples 2 to 6)
Rare earth magnets of Examples 2 to 6 were produced in the same manner as in Example 1 except that the pretreatment liquid was changed so that the concentration of potassium pyrophosphate was the value shown in Table 1.

(Comparative Example 1)
A rare earth magnet of Comparative Example 1 was produced in the same manner as in Example 1 except that potassium pyrophosphate was not added to the pretreatment liquid.

(Comparative Example 2)
A rare earth magnet of Comparative Example 2 was produced in the same manner as in Example 1 except that the pretreatment liquid was adjusted to a potassium pyrophosphate concentration of 110 g / L (pyrophosphate ion concentration of 58.0 g / L). went.

(Example 7)
The rare earth magnet of Example 7 was produced in the same manner as in Example 1 except that the copper plating solution had the following composition and was adjusted to pH 8.5 and a bath temperature of 40 ° C. went. The composition of the copper plating solution is as follows.
Potassium pyrophosphate: 300 g / L
Copper pyrophosphate trihydrate: 75 g / L
28% aqueous ammonia: 3.0 mL / L

  The pyrophosphate ion concentration in the copper plating solution is 195 g / L, and the pyrophosphate ion concentration in the pretreatment solution is 63.3 g / L. Therefore, the pyrophosphate ion concentration ratio is 0.32. there were. This value is also shown in Table 2 (the same applies to the following examples and comparative examples).

(Examples 8 to 12)
Rare earth magnets of Examples 8 to 12 were produced in the same manner as in Example 7, except that the pretreatment liquid was changed so that the concentration of potassium pyrophosphate became the value shown in Table 2.

(Comparative Example 3)
A rare earth magnet of Comparative Example 3 was produced in the same manner as in Example 7 except that potassium pyrophosphate was not added to the pretreatment liquid. However, in Comparative Example 3, copper plating could not be performed, A rare earth magnet having a copper plating layer formed on the surface of the magnet body could not be obtained.

(Comparative Example 4)
The rare earth magnet of Comparative Example 4 was produced in the same manner as in Example 7 except that the pretreatment liquid was adjusted to a potassium pyrophosphate concentration of 110 g / L (pyrophosphate ion concentration of 58.0 g / L). went.
[Characteristic evaluation]

  Hereinafter, about the rare earth magnet obtained in Examples 1-12 and Comparative Examples 1-4, the adhesiveness with respect to the magnet body of these copper plating layers and the repeated usability of a copper plating solution were evaluated. The obtained results are shown in Table 1 (Examples 1-6, Comparative Examples 1-2) and Table 2 (Examples 7-12, Comparative Examples 3-4), respectively. Tables 1 and 2 show the results obtained in both cases where the temperature of the pretreatment liquid was 18 ° C and 25 ° C.

(Evaluation of adhesion of copper plating layer)
First, in order to evaluate the adhesion of the copper plating layer in the rare earth magnets obtained in Examples 1 to 12 and Comparative Examples 1 to 4, the surface of each rare earth magnet was evaluated for adhesion as shown below. A nickel plating layer as a protective layer was further formed.

That is, after washing each rare earth magnet with water, they are immersed in a nickel Ni plating solution and electroplated until the thickness of the nickel plating layer reaches 8 μm under the condition of a current density of 0.2 A / dm ^2. went. As the nickel plating solution, the concentration of nickel sulfate hexahydrate is 300 g / L, the concentration of nickel chloride hexahydrate is 45 g / L, the concentration of boric acid is 35 g / L, and the pH is 4.0. A bath temperature adjusted to 45 ° C. was used.

  The rare earth magnets of Examples 1 to 12 and Comparative Examples 1 to 4 in which the nickel plating layer was formed in this way were each subjected to heat treatment at 200 ° C. for 1 hour using an oven, and then immediately heated to about 10 ° C. It was quenched by being immersed in pure water, and it was visually confirmed whether or not the plating layer (copper plating layer and Ni plating layer) was blistered by this thermal shock.

  In Tables 1 and 2, A indicates a case where no blistering occurred, and B indicates a case where blistering occurred. In addition, when the plating layer is blistered, peeling is generated between the magnet body and the copper plating layer due to thermal shock, which means that the adhesion of the copper plating layer to the magnet body is weak.

  Moreover, in order to evaluate adhesiveness quantitatively, the following test was done. That is, first, two cuts having a width of 10 mm, a depth of 30 to 40 μm, and a length of 20 mm were made in parallel on the surface of each rare earth magnet. Next, a cut was made substantially vertically so as to tie two cuts in the vicinity of one end of these cuts. Then, the plating layer (copper plating layer and Ni plating layer) is peeled off in a direction perpendicular to the surface of the rare earth magnet from the cut formed substantially perpendicularly, and the force (vertical peel strength (gf / Cm)). In addition, this peeling was performed so that peeling might arise between a magnet element | base_body and a copper plating layer.

(Evaluation of repeated use of copper plating solution)
Production of the rare earth magnets of Examples 1 to 12 and Comparative Examples 1 to 4 described above was repeated 1000 times using the same pretreatment liquid, copper plating liquid and nickel plating liquid, respectively. At this time, the pyrophosphate ion concentration in the copper plating solution was measured by ion chromatography every 200 times. Then, when the concentration of pyrophosphate ions was reduced by 10% or more with respect to the unused state, potassium pyrophosphate was added to the copper plating solution, and the concentration before use was adjusted. And by such operation, the case where the adjustment of the pyrophosphate ion concentration in the copper plating solution was possible during 1000 repetitions was evaluated as A, the pyrophosphate ion concentration was increased, and the adjustment was When it became impossible, it evaluated as B.

  As shown in Tables 1 and 2, the rare earth magnets obtained in Examples 1 to 12 using a pretreatment liquid having a specific pyrophosphate ion concentration did not contain pyrophosphate ions or pyrophosphate ions Compared with Comparative Examples 1 to 4 in which the concentration of copper was low, there was no blistering of the plating layer, and since the adhesion strength of the plating layer to the magnet body was high, the copper plating layer and the magnet body were highly adhered It was confirmed that the property was obtained.

It is a perspective view which shows an example of the rare earth magnet obtained by the manufacturing method of this invention. It is a figure which shows typically the cross-sectional structure which follows the II-II line | wire of the rare earth magnet shown in FIG. It is a flowchart which shows the manufacturing process of the rare earth magnet of suitable embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Rare earth magnet, 2 ... Magnet body, 4 ... Copper plating layer.

Claims (3)

A magnet body containing a rare earth element, and a copper plating layer formed on the surface of the magnet body, a method for producing a rare earth magnet,
A pretreatment step of attaching a pretreatment liquid containing potassium pyrophosphate and / or sodium pyrophosphate and having a pyrophosphate ion concentration of 60 g / L or more to the magnet body;
Plating using a copper plating solution containing copper ions and pyrophosphate ions on the magnet body after the pretreatment step, and forming a copper plating layer on the surface of the magnet body; and
A method for producing a rare earth magnet, comprising:   2. The production of a rare earth magnet according to claim 1, wherein the concentration of pyrophosphate ions in the pretreatment solution is 1.2 times or less than the concentration of pyrophosphate ions in the copper plating solution. Method.   The method for producing a rare earth magnet according to claim 1, wherein the cooled pretreatment liquid is used.

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